In the anime

Stunfisk lays flat against the ground and closes its eyes. Its body then changes color to match the ground's colors. When it opens its eyes again, the colors on its body fade away and back to its original colors.

Trivia

Kecleon is able to blend in with its surroundings with its Ability Color Change. However, it is unable to learn Camouflage. This is possibly because Color Change would likely change Kecleon's type just after it had used Camouflage.

No Generation II or III Pokémon can learn this move (with the obvious exception of Smeargle).